3-carbocyclic-5,5-dialkyl-2-imidazolidinethiones

ABSTRACT

3-Carbocyclic-5,5-dialkyl-2-imidazolidinethiones useful as intermediates and accelerators of vulcanization of chloroprene rubbers.

United States Patent 1191 DAmico etal.

1451 Apr. 17, 1973 3-CARBOCYCLIC5,S-DIALKYL-Z- IMIDAZOLIDINETHIONES [75]Inventors: John Joseph DAmico, Akron; Darrell Dexter Mullins, Norton,both of Ohio [73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: Sept. 21, 1970 [21-] April/No.2 74,145

260/563 C, 260/574, 260/577, 260/784 [51 Int. Cl. ..C07d 49/30, C07d49/34 [58] Field of Search ..260/309.7

, [56] i 4 References Cited UNl'lED STATES PATENTS 3,174,975 3/l965Langis et a]. ..260/309.6

Allen et al., Plant Physiology, Vol. 26, Pages 61 l- 624 (1951). 1

Primary Examiner-Natalie Trousof Attorney-Richard O. Zerbe, J. E.M'aurer and Neal E.

Willis [57] ABSTRACT 3-Carbocyclic-5,5-dialkyl-2-imiclazolidinethionesuseful as intermediates and accelerators of vulcanization of chloroprenerubbers. 1

2 Claims, N0 Drawings S-CARBOCYCLlC-S ,5-DlALKYL-2-lIMlDAZOLIDINETHIONES X GIL-Ly R-N NH wherein x and y are lower alkyl ofone to six carbon atoms and R is a carbocyclic radical either aryl oralicyclic, for example, cyclopentyl, cyclohexyl, cyclooctyl,cyclododecyl, phenyl, monohalogen substituted phenyl, dihalogensubstituted phenyl, lower alkoxy substituted phenyl, p-anilino phenyland lower alkyl phenyl such as tolyl and xylyl. The compounds may alsobe represented by the tautomeric modification of the foregoing formulaas follows:

but the experimental evidence from infrared and nuclear magneticresonance spectral analysis indicates that they are predominatelyin thethione form.

' The new compounds form by heating the diamine with CS The preparationof the compounds is illustrated by the following non-limitativeexamples.

EXAMPLE 1 5,S-Dimethyl-3-phenyl-2-imidazolidinethione There was added inone portion 60.8 grams (0.6 mole) of carbon bisulfide to a stirredsolution of 49.3 grams (0.3 mole) of N-(2-ami'no-2-methyl)propylaniline, 150 ml. of ethyl alcohol and two drops ofpiperidine. The mixture was heated at refluxing temperature (47-68C.)for 24 hours, cooled to C., and then stirred at 0-10C. .for an hour.After filtering, the product was air-dried at 25-30C. giving a whitesolid, melting point 171172C. in 86.5 percent yield. Uponrecrystallization from alcohol, the melting point was unchanged. Theproduct analyzed 13.43 percent nitrogen and 15.57% sulfur compared to13.58 percent nitrogen and 15.54 percent sulfur calculated fOl'CnHmNgS.

EXAMPLE 2 5,5-Dimethyl-3-p-fluorophenyl-2- imidazolidinethione There wasadded in one portion 41.8 grams (.55 mole) of carbon bisulfide to astirred solution of 45.6 grams (0.25 mole) ofN-(2-amino-2-methyl)propyl-pfluoroaniline, 100 milliliters of ethylalcohol, and three drops of piperidine. The mixture was heated atrefluxing temperature for 24 hours, cooled to 0C., stirred at -10C. toobtain 55 grams product, melting point ll 82C. in 98 percent yield. Uponrecrystallization from alcohol the melting point was unchanged. Theproduct analyzed 12.27 percent nitrogen and 14.23 percent sulfur ascompared to 12.49 percent nitrogen and 14.30 percent sulfur calculatedfor C H N SF.

EXAMPLE 3 5,5-Dimethyl-3-o-fluorophenyl-I2- imidazolidinethione In theprocedure of Example 2, the amine is replaced by N-(2-amino-2-methy1)propyl-o-fluoro aniline.

There is obtained 55 grams product, melting point 2l922lC. in 98 percentyield. The melting point after recrystallizing from chloroform is223-224C. It contains 12.39 percent nitrogen and 14.24 percent sulfur ascompared to calculated values of 12.49 percent nitrogen and 14.30percent sulfur.

EXAMPLE 4 5 ,5-Difnethyl-3-(4-anilin0phenyl)-2- imidazolidinethione 41.8Grams of carbon bisulfide were added in one portion to a solution of63.8 grams (0.25 mole) of N- (2-amino-2'methyl)propyl-p-anilino aniline,100 m1. of ethyl alcohol, and three drops of piperidine. The procedurewas the same as in Example 2. There was obtained 72 grams of product,melting point 25025 1C. After recrystallization from acetone, themelting point was unchanged. The yield was 96 percent. The productcontained 14.16 percent nitrogen and 10.72 percent sulfur as compared tocalculated values of 14.13 percent nitrogen and 10.78 percent sulfur.

EXAMPLE 5 5 ,5 -Dimethyl-3-o-tolyl-2-imidazolidinethione There was addedin one portion 41.8 grams (0.55 mole) of carbon bisulfide to a mixtureof 44.6 grams (0.25 mole) of N-(2-amino-2-methyl)propyl-otoluidine, 100ml. of ethyl alcohol, and three drops of piperidine. The charge washeated at refluxing temperature for 24 hours, cooled to 0C., filtered,washed with 100 ml. of heptane, and air dried at 25-30C. There wasobtained 52 grams, melting point 233-4. The melting point was 234-5after recrystallization from chloroform. The yield was: 94.5 percentfTheproduct contained 12.32 percent nitrogen and 14.16 percent sulfur ascoinpared to calculated values of 12.72 percent nitrogen and 14.55percent sulfur.

EXAMPLE 6 5,5-Dimethyl-3-metatolyl-2-imidazolidinethione In theprocedure of Example 5, there was substituted for the amine reactant alike quantity of N-(2-amino-2- methyl)propyl-m-toluidine. There wasobtained 50 grams of product, melting point 168.0l68.5C. The meltingpoint after recrystallizing from alcohol was 168.0l68.5C. The yield was90.5 percent. The product contained 12.56 percent nitrogen and 14.08percent sulfur as compared to 12.72 percent nitrogen and 14.55 percentsulfur.

EXAMPLE 7 5,5-Dimethyl-3-p-tolyl-2-imidazolidinethione In the procedureof Example 6 there was substituted for the amine a like quantity ofN-(2-amino-2- methyl)propyl-p-toluidine. There was obtained 53 grams,melting point 195-196C. The melting point remained unchanged afterrecrystallizing from alcohol. The product obtained in 96.5 percentyield, contained 12.57 percent nitrogen and 14.32 percent sulfur ascompared to calculated values at 12.72 percent nitrogen and 14.55percent sulfur.

EXAMPLE 8 5,5-Dimethyl-3-p-chlorophenyl-2- imidazolidinethione 41 .8Grams (0.55 mole) of carbon bisulfide was added in one portion to asolution of 49.7 grams (0.25 mole) ofN-(2-amino-2-methyl)-propyl-pchloroaniline, 100 ml. of ethyl alcohol,and three drops of piperidine. The heat of reaction caused temperatureto rise from 28 to 33C. The mixture was stirred and heated at refluxingtemperature for 24 hours, cooled at C., stirred at 0-l0 for 30 minutesand the solids removed by filtration and dried at 2530C. There wasobtained 45 grams, melting point l67-9C. The melting point afterrecrystallizing from alcohol was 169] 7 0C. Product obtained in 74.5percent yield, contained 12.19 percent nitrogen and 13.46 percent sulfuras compared to calculated values of l 1.64 percent nitrogen and 13.3percent sulfur.

EXAMPLE 9 5,5-Dimethyl-3-(3,4-dichlorophenyl)-2- 'imidazolidinethioneThere was added in one portion 33.3 grams (0.44 mole) of carbonbisulfide to a solution of 46.7 grams (0.2 mole) ofN-(2-amino-2-methyl)propyl-3,4- dichloroaniline, 100 ml. of ethylalcohol, and three drops of piperidine. The heat of reaction caused thetemperature to rise from 24 to 28C. The reaction mixture was stirred andheated at refluxing temperature for 24 hours, cooled to 0C., stirred at0l0C. for 30 minutes, the solids filtered and dried in air 25-30C. Therewas obtained 48 grams, melting point l90195 C. in 87 percent yield.After recrystallizing from alcohol, the melting point was 220-221C. Theproduct contained 10.1] percent nitrogen and 11.85 percent sulfur ascompared to calculated values of 10.18 per cent nitrogen and 1 1.65percent sulfur.

EXAMPLE l0 5,5-Dimethyl-3-(p-ethoxyphenyl)-2- imidazolidinethione 4There was added in one portion 41.8 grams (0.55 mole) of carbonbisulfide to a solution of 52.1 grams (0.25 mole) ofN-(2-amino-2-methyl)propyl-p-ethoxy aniline, 100 ml. of ethyl alcohol,and three drops of piperidine. The temperature rose from 3039C. due tothe heat of reaction. The reaction mixture was heated at refluxingtemperature (5357C) for 24 hours, cooled to 0C., stirred at 0-l0C. for30 minutes, and the solids collected by filtration and air dried at25-30C. There was obtained 60 grams, melting point l95l96C. Afterrecrystallizing from ethyl alcohol, the product melted at 20l202C. Theyield was 95.5 percent of product analyzing 10.94 percent nitrogen and12.71 percent sulfur as compared to l 1.19 percent nitrogen and 12.81percent sulfur calculated for C H N OS.

EXAMPLE 1 1 5,5-Dimethyl-3-cyclohexyl-2-imidazolidinethione The aminerequired for this example was prepared by the method of M. Senkus, J.Am. Chem. Soc. 68, 10-12, (1946). Replacing the nitro amine by N-(2-amino-Z-nitropropyl)cyclo-hexylamine, there wasobtained in 46.7 percentyield, N-(2-amino-2-methylpropyl)cyclohexylamine, b.p. 1l4116C./15 mm.To a solution of 34 grams (0.2 mole) of this amine, 100 ml. of ethylalcohol and three drops of piperidine there was added dropwise, 16.8grams (0.22 mole) of carbon bisulfide. The heat of reaction caused thetemperature to rise from 25 to 34C. The procedure was the same asExample 10. 5,S-Dimethyl-3-cyclohexyl-2-imidazolidinethione was obtainedin 70.6 percent yield, melting point 242244C. The melting point afterrecrystallization from DMF was 246247C. Analysis gave 13.20 percentnitrogen and 14.87 percent sulfur as compared to 13.19 percent nitrogenand 15.10% sulfur calculated for C H N S.

In another procedure 16.8 grams (0.22 mole) of carbon bisulfide wasadded dropwise to a solution of 34 grams (0.2 mole) ofN-(2-amino-2-methylpropyl)cyclohexylamine containing 2 ml. of sodiumhypochlorite. Using the same procedure as above, the yield was.94.4-percent' of said product melting at 246247C. Upon recrystallizationfrom 300 'ml.

dimethylformamide/lOO ml. water the melting point remained unchanged.The analysis gave 13.07 percent nitrogen and 14.59 percent sulfur.

The chloroprene rubbers known commercially as neoprene are polymers of2-chloro-l ,3-butadiene (chloroprene) and copolymers of chlororprenewith dienes or vinyl compounds in which chloroprene comprises thepredominant monomer. They are vulcanizable with certain metal oxides,examples of which are magnesium oxide, lead oxide and zinc oxide. Thetemperature of vulcanization is within the range of 20 0C. and usually160C. The new accelerators may be utilized in stocks containing any ofthe usual chloroprene rubber vulcanizing agents and with carbon black orlight fillers. The accelerator may be as little as 0.05 parts by weightper 100 parts by weight or above the minimum viscosity is recorded.Longer times are indicative of greater processing safety. The stocks arecured for the length of time required to obtain the optimum cure. Thecure temperature is 153C. Curing characteristics are determined by meansof the Monsanto Oscillating Disc Rheometer described by Decker, Wise andGuerry in Rubber World, Dec. 1962, page 68. From the Rheometer data thetime to optimum cure is determined and the stocks are cured in a pressfor that time. The ultimate tensile strength and modulus at 300 percentelongation are determined for each vulcanizate. v

Atypical neoprene rubber stock was compounded comprising:

. Parts by Weight Neoprene W 100.0 Magnesium oxide 4.0 Phenyl alphanaphthylamine 2.0 Stearic acid 0.5 SRF carbon black 75.0 Hydrocarbonsoftener 15.0 Zinc Oxide 5.0

To each of the several portions of the base stock was added 0.5 part byweight of accelerator as indicated below. Comparison to stock F and Gshows the effect of the carbocyclic and alkyl substituents.

Accelerator 5,5-Dimethyl-3-phenyl-2-imidazolidinethione5,5-Dimethyl-3-(p-ethoxyphenyl )-2- imidazolidinethione 5 ,5-Dimethyl-3-p-chiorophenyl-2- imidazolidinethione 5 ,5 -Dimethyl-3-(3,4-dichlorophenyl-2- imidazolidinethione 5 ,5-Dimethyl-3-cyclohexyl-2-imidazolidinethione 3-Phenyl-Z-imidazolidinethione 5,5-Dimethyl-2-imidazolidinethione ock are m U 0 w 9 The physicalproperties of the respective stocks at optimum cure are given in thefollowing table.

TABLE I g Cure Modulus Tensil at Break Mooney Time in at 300% Break inElong. Scorch Stock Minutes Elong. lbs/in t, A 50 2700 280 25.8 B 552750 2800 300 27.0 C 40 2620 2700 300 28.0 D i 45 2470 2600 310 38.0 E80 2200 270 28.7 F 40 2840 2600 300 15.7 G 50 2700 240 11.5

A series of vulcanizates were prepared using the following base stock:

Parts by Weight Neoprene W 100.0

SRF carbon black 75.0 Hydrocarbon softener l'5.0 Stearic acid 0.5 vPhenyl alpha naphthylamine 2.0 Magnesium oxide 4.0

To the above base stock was added in separate stoc s 0.5 part by weightof accelerator as indicated below:

Accelerator 5 ,5-Dimethyl-3-phenyl-Z-imidazolidinethione 5,5-Dimethyl-3-p-fluorophenyi-2- imidazolidinethione 5,5-Dimethyl-3-o-fluorophenyl-2- imidazolidinethione5,5-Dimethyl-3-(4-anilinophenyl )-2- imidazolidinethione 5,S-Dimethyl-3-o-tolyl-2-imidazolidinethione 5,5-Dimethyl-3-m-tolyi-Z-imidazolidinethione 5,S-Dimethyl-3-p-tolyl-2-imidazolidinethione The tensile properties ofthe vulcanizates at the 60 minute cures and resistance of theunvulcanized compositions to scorch are set forth in Table ll.

TABLE 11 Tensile at Ult. Mooney Break in Eiong. Scorch Stock lbs/in t H2700 270 8 .0 J 2700 280 9.3 K 2400 280 10.5 L 2400 280 l 3 .2 M 2000290 12.3 N 2700 270 8 .3 P 2400 280 9.2

where R is cycloalkyl of five to 12 carbon atoms [or aryl selected fromthe group consisting of phenyl, monohalophenyl, dihalophenyl, mono(lowera1 kyl)phenyl, di(lower alkyl)phenyl, lower alkoxyphenyl andanilinophenyl] and Y [y] is lower alkyl.

2. A compound of claim 1 wherein Y [y] is methyl and R is cyclohexyl.

F ORM PO-105O (10-59) V UNITED STATES PATENT OFFICE 5 CERTIFICATE OFCORRECTION Patent No. 3 7Z8 355 Dated April 17 19 73 Inventofls) JohnJoseph D'Amico and Darrell Dexter Mullins It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 4, line 48, "chlororprene" should read chloroprene-.

Column 4, line 58, "or" should read of-.

Column 6, lines 38-52, Claims 1 and 2, the material appearing in brackets should be deleted so that the claims read:

1. 5-Carbocyclic-5,5di(lower alkyl)2- imidazolidinethione of the formulawhere R is cycloalkyl of 5 to 12 carbon atoms and Y is lower alkyl.

2. A compound of claim 1 where Y is methyl and R is cyclohexyl.

Siggned and sealed this 31st day of December 1974.

(SEAL) Attest MCCOY M. GIBSON JR. C. MARSHALL DAN?! Attesting OfficerCommissioner of Patents USCOMM-DC sows-P69 U.5i GOVERNMENT PRINTINGOFFICE: 1969 O355"334

2. A compound of claim 1 wherein Y (y) is methyl and R is cyclohexyl.